In　this　paper,　the　aerodynamic　performance　of　a　Hex-rotor　unmanned　aerial　vehicle　(UAV)　with　different　rotational　speeds　(1500-2300　RPM)　considering　the　horizontal　airflow　conditions　is　analyzed　by　both　simulations　and　experiments.　A　low-speed　wind　tunnel　experiments　platform　is　applied　to　measure　the　thrust,　torque,　and　power　consumption　of　a　Hex-rotor　UAV　with　different　rotational　speeds　in　horizontal　airflow,　which　varied　from　0　m/s-4　m/s.　First,　this　paper　introduces　the　effect　of　horizontal　airflow　on　a　UAV.　Then,　the　low-speed　wind　tunnel　experiments　were　carried　out　on　a　Hex-rotor　UAV　(D/L　=　0.56)　with　different　horizontal　velocities　to　determine　the　hover　performance.　Finally,　numerical　simulations　were　obtained　with　the　streamline　distributions,　pressure　distributions,　velocity　contour,　and　vortex　distributions　at　different　horizontal　airflow　conditions　to　describe　the　aerodynamic　interference　effect　of　different　horizontal　airflows.　Combined　with　the　experimental　results　and　numerical　simulations　results,　the　horizontal　airflow　proved　to　have　a　significant　influence　on　the　aerodynamic　performance　of　the　Hex-rotor　UAV　with　an　increase　in　thrust　and　power.　Indeed,　the　streamlines　in　the　flow　field　were　coupled　to　each　other　at　the　presence　of　the　incoming　airflow.　Especially　when　the　incoming　airflow　was　larger,　the　Hex-rotor　UAV　could　properly　use　low-speed　flight　to　maintain　high　power　loading.　Finally,　it　is　inferred　that　the　aerodynamic　performance　of　the　Hex-rotor　UAV　is　also　related　to　the　movement　and　deformation　of　the　vortex　at　the　tip　of　the　rotor.　©　2019　by　the　authors.